(-)-Bisnorcymserine (BNC) tartrate is a small synthetic compound developed within IRP, NIA, for the treatment of late stage Alzheimer?s disease has recently entered clinical evaluation. It is a brain penetrant selective reversible butyrylcholinesterase inhibitor. This Task Order relates to evaluation of the level of percent inhibition of the target enzymes butyryl- and acetylcholinesterase in frozen blood and plasma samples derived from the initial BNC Phase 1 clinical trial (BNC doses 20 mg orally and escalations thereof). These studies allow analysis of drug target engagement during the initial evaluation of the drug in healthy elderly volunteers under an approved clinical protocol.